208 MYOLOGY. 



nally and longitudinally, the lesser ones diverging from it inwards 

 and forwards. 



OHgin. — The chief bundle arises from the inferior sacro-iliac 

 ligament at tjie angle of the sacrum, passing directly forwards. 



Insertion.—l^' the posterior border of the last rib, becoming 

 attached in its bourse to the free extremities of the transverse 

 processes of the lumbar vertebrae. The other bundles leave the- 

 internal border of the first, and are attached to most of the trans- 

 verse processes of the lumbar vertebrae, and inner surfaces of the 

 last two or three ribs. 



Relation. — Superiorly with the vertebrse, and intertransversales 

 lamborum ; inferiorly with the psoas magnus. 



Action. — To assist in lateral flection of the lumbar vertebrae, 

 and to draw the last ribs backwards. 



DiAPHKAGMATIC REGION. 



This region contains only one muscle, from which it takes it« 

 name. 



DIAPHRAGM. 



{Diaphragma.) 



(Fig. 77. A.) 



The diaphragm, or midrif, is the muscular partition which 

 separates the thorax from the abdomen ; it slopes obliquely down- 

 wards and forwards, and is in form elliptical, or somewhat heart- 

 shaped, being widest superiorly. The thoracic surface is convex 

 and covered with pleura, the abdominal concave and covered with 

 peritoneum. It is divided into a body or septum, and two crura 

 or appendices; the body, or greater muscle, is made up of a fleshy 

 periphery and tendinous phrenic centre (Speculuvo Helmontii). 



Attachments. — The fleshy portion is attached to the inner 

 surface of the distal ends of the last twelve ribs, or to their 

 cartilages, and to the superior surface of the ensiform cartilage, 

 the fibres converging towards the tendinous centre. The crura or 

 pillars, two in number, lie below the vertebrae in the sublumbar 

 region. The right is the longer and larger, and arises from the 

 inferior surface of the bodies of all the lumbar vertebrae but the 

 last, by strong tendinous fibres which blend with the inferior 

 common ligament. The left differs from the right in arising 

 from only one or two anterior lumbar vertebrae. The crura pass 



